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Over the last 20 years, flue gas desulfurization gypsum (FGD gypsum) has become a valuable and widely used substitute for a natural raw material to produce plasters, mortars, and many other construction products. The essential advantages of FGD gypsum include its high purity and stability, which allow for better technical parameters compared to natural gypsum, and, until recently, its low price and easy availability. This FGD gypsum is obtained in the process of desulfurization of flue gases and waste gases in power plants, thermal power plants, refineries, etc., using fossil fuels such as coal or oil. The gradual reduction in energy production from fossil raw materials implemented by European Union countries until its complete cessation in 2049 in favor of renewable energy sources significantly affects the availability of synthetic gypsum, and forces producers of mortars and other construction products to look for new solutions. The gypsum content in commonly used light plaster mortars is usually from 50 to 60% by mass. This work presents the results of tests on mortars wherein the authors reduced the amount of gypsum to 30%, and, to meet the strength requirements specified in the EN 13279-1:2008 standard, added Portland cement in the amount of 6–12% by mass. Such a significant reduction in the content of synthetic gypsum will reduce this raw material's consumption, thus extending its availability and developing other solutions. The study presented the test results on strength, density, porosity, pore size distribution, and changes in the microstructure of mortars during up to 180 days of maturation in conditions of increased relative humidity. The results show that decreased porosity and increased mechanical strength occur due to the densification of the microstructure caused by the formation of hydration products, such as C-S-H, ettringite, and thaumasite. [ABSTRACT FROM AUTHOR]

The production of flue gas desulfurization gypsum poses a serious threat to the environment. Thus, utilizing gypsum-based self-leveling mortar (GSLM) stands out as a promising and effective approach to address the issue. β-hemihydrate gypsum, cement, polycarboxylate superplasticizer, hydroxypropyl methyl cellulose ether (HPMC), retarder, and defoamer were used to prepare GSLM. The impact of mineral admixtures (steel slag (SS), silica fume (SF), and fly ash (FA)) on the physical, mechanical, and microstructural properties of GSLM was examined through hydration heat, X-ray diffractometry (XRD), Raman spectroscopy, and scanning electron microscopy (SEM) analyses. The GSLM benchmark mix ratio was determined as follows: 94% of desulfurization building gypsum, 6% of cement, 0.638% each of water reducer and retarder, 0.085% each of HPMC and defoamer (calculated additive ratio relative to gypsum), and 0.54 water-to-cement ratio. Although the initial fluidity decreased in the GSLM slurry with silica fume, there was minimal change in 30 min fluidity. Notably, at an SS content of 16%, the GSLM exhibited optimal flexural strength (6.6 MPa) and compressive strength (20.4 MPa). Hydration heat, XRD, and Raman analyses revealed that a small portion of SS actively participated in the hydration reaction, while the remaining SS served as a filler. [ABSTRACT FROM AUTHOR]

[Display omitted] Carbon capture and desulfurization of flue gases are crucial for the achievement of carbon neutrality and sustainable development. In this work, the "one-step" adsorption technology with high-performance metal–organic frameworks (MOFs) was proposed to simultaneously capture the SO 2 and CO 2. Four machine learning algorithms were used to predict the performance indicators (N CO2+SO2 , S CO2+SO2/N2 , and TSN) of MOFs, with Multi-Layer Perceptron Regression (MLPR) showing better performance (R 2 = 0.93). To address sparse data of MOF chemical descriptors, we introduced the Deep Factorization Machines (DeepFM) model, outperforming MLPR with a higher R 2 of 0.95. Then, sensitivity analysis was employed to find that the adsorption heat and porosity were the key factors for SO 2 and CO 2 capture performance of MOF, while the influence of open alkali metal sites also stood out. Furthermore, we established a kinetic model to batch simulate the breakthrough curves of TOP 1000 MOFs to investigate their dynamic adsorption separation performance for SO 2 /CO 2 /N 2. The TOP 20 MOFs screened by the dynamic performance highly overlap with those screened by the static performance, with 76 % containing open alkali metal sites. This integrated approach of computational screening, machine learning, and dynamic analysis significantly advances the development of efficient MOF adsorbents for flue gas treatment. [ABSTRACT FROM AUTHOR]

Heavy metals in flue gas desulfurization (FGD) gypsum from coal-fired power plants are at risk of releaching during the processes of stockpiling and resource utilization. In this study, the effects of organosulfur chelators dithiocarbamate (DTC) and trisodium trithiocyanate-15 (TMT-15) on the solidification characteristics of heavy metals in desulphurized gypsum under different mass fractions, pH values, water contents and reaction times were investigated. The chemical composition and morphology were analyzed by inductively coupled plasma atomic emission spectrometer (ICP-AES) and scanning electron microscope (SEM). The experiments showed that both DTC and TMT-15 were effective at stabilizing the heavy metals in the FGD gypsum, with more than a 50% curing effect for all the heavy metals except Pb. DTC showed a better stabilization for Pb, Hg, Cu, Zn, and Cr, and TMT-15 showed a better curing effect for Cd. The solidified gypsum had good heavy metal stability in low-water-content environments. Increasing the mass fraction, reaction time, and pH decreased the heavy metal leaching, and the mass fraction had the greatest effect on the total heavy metal leaching concentration, followed by the reaction time and pH value. [ABSTRACT FROM AUTHOR]

To effectively reduce SO2 emissions, flue gas desulfurization methods are widely used in coal‐fired power plants. In desulfurization, the dry sorbent injection (DSI) technology has the advantages of high desulfurization efficiency, simple operation, convenient adjustment, and low initial investment. Here, a pilot‐scale experimental system was designed and built to investigate the desulfurization characteristics of the DSI technology. The influence of the residence time of the desulfurizer, the reaction temperature, the stoichiometric ratio of the desulfurization reaction, the particle size of the desulfurizer, the inlet SO2 concentration, the dust concentration, and the water vapor content in the flue gas on the desulfurization efficiency at low SO2 concentrations was studied by injecting NaHCO3 into the pipeline. The desulfurization efficiency can be significantly improved by reducing the desulfurizer particle size or increasing the water vapor content in the flue gas at low SO2 concentration. An empirical formula describing the dependence of the desulfurization efficiency on experimental parameters is given. [ABSTRACT FROM AUTHOR]

This research examines the behavior of electrochemical passivation and the chemistry of surface films on 654SMO super austenitic stainless steel and C276 nickel-based alloy in simulated condensates from flue gas desulfurization in power plant chimneys. The findings indicate that the resistance to polarization of the protective film on both materials initially rises and then falls with either time spent in the solution or the potential of anodic polarization. Comparatively, 654SMO exhibits greater polarization resistance than C276, indicating its potential suitability as a chimney lining material. Mott–Schottky analysis demonstrates that the density of donors in the passive film formed on 654SMO exceeds that on C276, potentially due to the abundance of Fe oxide in the passive film, which exhibits the characteristics of an n-type semiconductor. The primary components of the passive films on both materials are Fe oxides and Cr oxides. The formation of a thin passive film on C276 in the simulated condensates is a result of the low Gibbs free energy of nickel oxide and low Cr content. The slower diffusion coefficient of point defects leads to the development of a thicker and more compact passive film on the surface of 654SMO. [ABSTRACT FROM AUTHOR]

There is an urgent need to address sulfur dioxide (SO2) from the burning of fossil fuels, which poses a serious hazard to the surrounding environment due to its emission. In this work, UiO-66-type metal–organic framework materials (MOFs) were prepared by hydrothermal method and applied to flue gas desulfurization. Through characterization analysis, it was found that UiO-66 sample had high crystallinity and good thermal stability. Besides, UiO-66 sample had a large specific surface area (1423 m2/g) and a large pore volume (0.69 cm3/g). In the desulfurization experiments of SO2/CO2/O2/N2 gas mixture (0.3/10.0/5.5/84.2 vol.%), UiO-66 had a breakthrough time of 137.6 min/g for SO2, the high selectivity of SO2/CO2 (36.0), and strong acid resistance. Besides, the adsorption thermodynamic analysis can confirm that the adsorption process of UiO-66 for SO2 was a combination of physical adsorption and chemical adsorption. At 1.0 bar and 298 K, the adsorption capacity of SO2 on UiO-66 reached 8.12 mmol/g. [ABSTRACT FROM AUTHOR]

Flue gas desulfurization gypsum (FGDG), a solid waste material generated by power plants, offers a cost-effective solution for preparing backfill materials. Concurrently, given that most backfill materials are exposed to mine water erosion, an investigation into the mechanical performance degradation and damage mechanisms of FGDG backfill materials subjected to prolonged chloride salt erosion is crucial for ensuring the stability of goaf backfills (by goaf, we mean the area or space that remains underground after the extraction of valuable minerals). This study explores the mechanical properties and damage mechanisms of backfill samples treated with varying concentrations of chloride. The findings indicate that over time, the mass of the sample initially decreases, experiences a slight increase, and then gradually declines. Simultaneously, the strength and structure of the sample deteriorate rapidly, followed by a partial recovery. The rebound in sample mass is attributed to an incomplete hydration reaction that continuously transforms free water into bound water. Microstructure analysis techniques, such as X-ray diffraction (XRD) and field-emission scanning electron microscopy (FE-SEM), reveals that the degradation in mechanical strength and structure is a consequence of chloride salt erosion. Subsequent reuse is facilitated by the formation of Friedel's salt resulting from the reaction between hydration products and chloride ions, filling voids in the sample and impeding further chloride ion erosion into the deeper regions. Notably, FGDG exhibits outstanding reuse performance in prolonged and high-concentration chloride ion environments. This study serves as a reference for understanding the deterioration mechanism and practical application of backfills in chloride-rich environments. [ABSTRACT FROM AUTHOR]

Since the signing of the Minamata Convention in 2013, attempts have been primarily focused on reducing the emission of elemental mercury (Hg0) from coal-fired power plants (CFPPs). The most cost-effective measure for controlling the emission of mercury involves oxidizing Hg0 to mercury oxides, which are then removed using wet flue gas desulfurization (WFGD). Thus, novel photocatalysts with the best properties of photocatalytic ability and thermal stability need to be developed urgently. In this study, titanium dioxide (TiO2)-based photocatalysts were synthesized through the modification of three metal oxides: CuO, CeO2, and Bi2O3. All the photocatalysts were further characterized using X-ray diffraction, X-ray photoelectron spectroscopy, photoluminescence, and ultraviolet-visible spectrometry. The photocatalytic oxidation efficiencies of Hg0 were evaluated under an atmosphere of N2 + Hg0 at 100–200 °C. The photocatalytic reactions were simulated by kinetic modeling using the Langmuir–Hinshelwood (L–H) mechanism. The results showed that Bi2O3/TiO2 exhibited the best thermal stability, with the best oxidation efficiency at 200 °C and almost the same performance at 100 °C. L–H kinetic modeling indicated that photocatalytic oxidation reactions for the tested photocatalysts were predominantly physical adsorption. Additionally, the activation energy (Ea), taking into account Arrhenius Law, decreased dramatically after modification with metal oxides. [ABSTRACT FROM AUTHOR]

This study focuses primarily on sulfur dioxide (SO2) emissions control problem in a wet flue gas desulfurization (WFGD) process, and our objective is to design an intelligent control system so that the outlet SO2 concentration satisfies the SO2 emission standard. In our approach, a multimodel control framework, which is made up of a linear robust controller and a neural controller, is integrated with the invasive weed optimization (IWO) algorithm in an elegant fashion and used for SO2 emissions control purposes. A case study is carried out based on operation data from a 600 MW coal-fired unit, and simulation results show that IWO-based automatic clustering can identify different operating modes in the WFGD process with high accuracy. Further, the established multimodel control system can remove SO2 emissions effectively. Experimental results show that SO2 emissions can be removed effectively with the proposed method, and this could provide engineering guidance to design a WFGD control system. [ABSTRACT FROM AUTHOR]

Flue gas desulfurization (FGD) is a critical process for reducing sulfur dioxide (SO2) emissions from industrial sources, particularly power plants. This research uses calcium silicate absorbent in combination with machine learning (ML) to predict SO2 concentration within an FGD process. The collected dataset encompasses four input parameters, specifically relative humidity, absorbent weight, temperature, and time, and incorporates one output parameter, which pertains to the concentration of SO2. Six ML models were developed to estimate the output parameters. Statistical metrics such as the coefficient of determination (R2) and mean squared error (MSE) were employed to identify the most suitable model and assess its fitting effectiveness. The random forest (RF) model emerged as the top-performing model, boasting an R2 of 0.9902 and an MSE of 0.0008. The model's predictions aligned closely with experimental results, confirming its high accuracy. The most suitable hyperparameter values for RF model were found to be 74 for n_estimators, 41 for max_depth, false for bootstrap, sqrt for max_features, 1 for min_samples_leaf, absolute_error for criterion, and 3 for min_samples_split. Three-dimensional surface plots were generated to explore the impact of input variables on SO2 concentration. Global sensitivity analysis (GSA) revealed absorbent weight and time significantly influence SO2 concentration. The integration of ML into FGD modeling offers a novel approach to optimizing the efficiency and effectiveness of this environmentally crucial process. [ABSTRACT FROM AUTHOR]

This study was carried out on an absorber in the body of flue gas desulphurization system (FGD) of a coal-fired power plant. In this study, efficiency losses caused by the clogging or breaking of the spray nozzles were examined. These abovementioned problems of spray nozzles are the most common among the many factors affecting the sulfur retention efficiency. Although energy and exergy analysis is very common to optimize the system efficiency of FGD units, failure of spray nozzles in absorbers might be the main reason in terms of low FGD units efficiency and low SO2 removal rates. In this study, firstly locations of clogged or damaged nozzles are determined by examining a total of 240 nozzles (3 × 80). After the replacement of the broken spray nozzles, increase in the efficiency of A-B, B-C, A-C and A-B-C spray lines were observed as 9.14%, 3.77%, 10.56%, 9.72%, respectively. Depending on the washing zone of the nozzles, if one nozzle is damaged, it causes the efficiency to decrease between 0.24% and 0.36%. [ABSTRACT FROM AUTHOR]

Flue gas desulfurization wastewater (FGDW) contained high concentration of chloride, which made it difficult to recycle or achieve zero liquid discharge (ZLD). Friedel's salt precipitation (FSP) method could effectively dislodge chloride from FGDW and was expected to achieve ZLD of FGDW. Effects of reaction conditions, reagents dosage and types on chloride removal efficiency of FSP method were investigated systematically by single factor tests. Results showed that chloride removal by FSP method was fast and basically completed in 60 min. A higher stirring speed (≥90 rpm) would enhance the dispersion and dissolution of reagents, which was beneficial to improve the chloride removal efficiency. Moreover, the dosage and types of reagents had significant influence on chloride removal and should be selected according to actual need. A two-stage FSP method was applied to avoid the negative effect caused by the presence of sulfate, by which the sulfate and chloride removal efficiency reached 98% and 60%, respectively, in the real FGDW treatment. Through SEM and XRD analysis, precipitates formed in Stage I and II were proved to be CaSO 4 and friedel's salt, which belonged to Ca-Al-layered double hydroxides. The kinetics of FSP method removed chloride was attempted to study, and inferred the reaction as third order reaction. FSP method has enormous potential to be applied in industrial wastewater treatment. [Display omitted] • Friedel's salt precipitation (FSP) method is a cost-efficient way to remove Cl-. • The influential factors of FSP method were investigated systematically. • A two-stage FSP method was employed to avoid the inhibition of SO 4 2- on Cl- removal. • The dosage and types of reagents had significant influence on chloride removal. • A preliminary test was attempted to study the kinetics of Cl- removal by FSP method. [ABSTRACT FROM AUTHOR]

Current study proposes an effective way to modify the properties of super-sulfated cement (SSC) paste and mortar with preheated flue gas desulfurization (FDG) gypsum at different temperatures and durations, and different sulfate compositions. Preheated FGDs with temperatures between 25 and 150 °C and durations between 0 and 24 h were used to replace 5, 10 and 15 mass/% of slag in SSC. Besides the ordinary Portland cement, the sodium hydroxide (NaOH) was also used as the alkali activator. Both anhydrite and sodium sulfate with five different contents were used to provide the ions of SO3 to react with the ions of Ca and Al released from slag during hydration to form ettringite. Experimental results showed that partial replacement of untreated FDG with either the specifically preheated FDG or the commercial sulfates noticeably enhanced the early hydration of modified SSC pastes with setting time being significantly shortened and increased the compressive strength, while the NaOH solution delayed the setting time and reduced the compressive strength. Microstructural examinations revealed that using partial preheated FDG or commercial anhydrite did not alter the hydrated components, but significantly enhanced the fractions and stabilized the crystallization of those hydrates with hydration time. [ABSTRACT FROM AUTHOR]

Studying the distribution and transport dynamics of cations in plants is crucial for understanding their response mechanisms to saline–alkali stress conditions. However, our current understanding of how restoration measures affect cation distribution and transport in plants is surprisingly limited. To address this gap, we conducted a split-plot experiment using Medicago sativa L. cv. "Zhongmu No. 1" to investigate the combined effects of biological and chemical restoration measures—with bio-fertilizer as the primary zone and flue gas desulfurization (FGD) gypsum and with humic acid as the secondary zone—on soil properties, plant growth, and the content, distribution, and transport of cations in plants. The results revealed that bio-fertilizers exhibited positive effects on the plant growth, yield, and translocation of key ionic components to leaves. On the contrary, FGD gypsum with humic acid reduced the soil's pH level, exchangeable sodium percentage (ESP), and sodium adsorption ratio (SAR) while increasing the contents of K+, Ca2+, and Mg2+ in the soil. The combination of bio-fertilizer, FGD gypsum, and humic acid increased the biomass and enhanced the translocation of Mg2+ to leaves. The distribution and transport of Mg2+ within the plant constituted pivotal elements for enhancing plant growth through restoration strategies. The application of bio-fertilizer, FGD gypsum, and humic acid reduced Na+ transport in M. sativa by enhancing the selective absorption of beneficial ions in leaves and by facilitating the transport of Ca2+ and Mg2+ from stems to the leaves. This, in turn, increases the salt tolerance of plants and promotes their growth. Our results offer new insights into the interactions among measures, soil, and plants in saline–alkali land restoration, providing practical solutions for the restoration of saline–alkali soil. [ABSTRACT FROM AUTHOR]

Persulfate liquid-phase advanced oxidation technology (AOP) has become a feasible and effective choice in wet flue gas desulfurization (WFGD) technology due to its efficient oxidation capacity and environmentally friendly characteristics. This paper proposes a new process for removing NO from simulated flue gas using FeⅡCA/heat co-activated persulfate system. The main influencing factors, active components, reaction products and reaction process of NO purification system were mainly studied. The results show that in the process of purifying NO in the system, active substances such as S 2 O 8 2-, •OH and •SO 4 - will be produced, among which •OH is the main free radical that oxidizes NO. The liquid phase products after the system absorbs and oxidizes NO are mainly NO 3 - and SO 4 2-, and the material balance before and after the reaction is satisfied. In the process of purifying NO, by increasing the concentration of persulfate and selecting an appropriate Fe2+/CA ratio, the NO purification effect of the system can be promoted. In addition, the purification effect is closely related to temperature. However, if the pH value of the solution is increased or the NO concentration is too high, the NO purification effect of the system will be reduced. For this reason, under suitable process conditions, the NO purification rate of the system can reach 71.1%. The experimental results confirmed the feasibility of FeⅡCA/heat co-activated persulfate to remove NO from flue gas, and provided a theoretical basis for further research and practical application of this system. [Display omitted] • A new process is proposed for citric acid complexing ferrous ions combined with heat coactivate persulfate to oxidize and absorb NO. • Citric acid improves the utilization of Fe2+ in the system, and hydroxyl radicals are the free radicals that play the main oxidation effect on NO in the system. • A material balance calculation was conducted on the reaction process, and the reaction pathway was identified. [ABSTRACT FROM AUTHOR]

Constructed wetlands (CWs) represent a natural wastewater treatment process, offering economic and environmental advantages. These systems can remove several components that may cause negative impacts on the environment. Media types and plant species are crucial influencing factors for the removal of contaminants in CWs. The goal of this study is to evaluate the capacity of a CW using Tamarix spp. with three filter media to treat FGD wastewater. Planted and unplanted CWs were set up with varying types of biofilm support media: 3 bioreactors were operated with 50% gravel and 50% zeolite (v/v), 3 with 100% gravel, and 3 with 50% gravel, 25% zeolite, and 25% silage. Planted CWs had the greatest potential to reduce the concentrations of B, K, and NH4+-N in 64.9%, 91.1%, and 92.5%, respectively, when used in addition to the filter composed by 50% gravel + 50% zeolite, which was the only media keeping the plants alive for 60 days. The results showed that the optimal selection of filter media depends on the purpose for which the treatment has been projected for, considering that the types of substrates influenced the nature of the contaminant removal in the CW. Salinity impact on Constructed wetlands (CWs) is still scarce in the literature. The novelty is the choice of a salt cedar (Tamarix spp.) combined with three filter media types ((1) gravel; (2) gravel and zeolite; (3) gravel, zeolite, and silage) to treat flue gas desulfurization wastewater in CWs. Our findings demonstrate that filter media containing 50% gravel + 50% zeolite can decrease the toxicity of contaminants from FGD wastewater in plants. [ABSTRACT FROM AUTHOR]

Flue gas desulfurization is crucial for both human health and ecological environments. However, developing efficient SO2 adsorbents that can break the trade‐off between adsorption capacity and selectivity is still challenging. In this work, a new type of fluorinated anion‐pillared metal–organic frameworks (APMOFs) with a pillar‐cage structure is fabricated through pillar‐embedding into a highly porous and robust framework. This type of APMOFs comprises smaller tetrahedral cages and larger icosahedral cages interconnected by embedded [NbOF5]2− and [TaOF5]2− anions acting as pillars. The APMOFs exhibits high porosity and density of fluorinated anions, ensuring exceptional SO2 adsorption capacity and ultrahigh selectivity for SO2/CO2 and SO2/N2 gas mixtures. Furthermore, these two structures demonstrate excellent stability towards water, acid/alkali, and SO2 adsorption. Cycle dynamic breakthrough experiments confirm the excellent separation performance of SO2/CO2 gas mixtures and their cyclic stability. SO2‐loaded single‐crystal X‐ray diffraction, Grand canonical Monte Carlo (GCMC) simulations combined with density functional theory (DFT) calculations reveal the preferred adsorption domains for SO2 molecules. The multiple‐site host–guest and guest‐guest interactions facilitate selective recognition and dense packing of SO2 in this hybrid porous material. This work will be instructive for designing porous materials for flue gas desulfurization and other gas‐purification processes. [ABSTRACT FROM AUTHOR]

Flue gas desulfurization is crucial for both human health and ecological environments. However, developing efficient SO2 adsorbents that can break the trade‐off between adsorption capacity and selectivity is still challenging. In this work, a new type of fluorinated anion‐pillared metal–organic frameworks (APMOFs) with a pillar‐cage structure is fabricated through pillar‐embedding into a highly porous and robust framework. This type of APMOFs comprises smaller tetrahedral cages and larger icosahedral cages interconnected by embedded [NbOF5]2− and [TaOF5]2− anions acting as pillars. The APMOFs exhibits high porosity and density of fluorinated anions, ensuring exceptional SO2 adsorption capacity and ultrahigh selectivity for SO2/CO2 and SO2/N2 gas mixtures. Furthermore, these two structures demonstrate excellent stability towards water, acid/alkali, and SO2 adsorption. Cycle dynamic breakthrough experiments confirm the excellent separation performance of SO2/CO2 gas mixtures and their cyclic stability. SO2‐loaded single‐crystal X‐ray diffraction, Grand canonical Monte Carlo (GCMC) simulations combined with density functional theory (DFT) calculations reveal the preferred adsorption domains for SO2 molecules. The multiple‐site host–guest and guest‐guest interactions facilitate selective recognition and dense packing of SO2 in this hybrid porous material. This work will be instructive for designing porous materials for flue gas desulfurization and other gas‐purification processes. [ABSTRACT FROM AUTHOR]

• FGD-gypsum as an in-house PL amendment to reduce P solubility was investigated. • Commercial PLT was less effective in reducing P solubility compared to FGD-gypsum treatment. • Toxic metal concentrations were negligible in FGD gypsum and have no environmental concern. • FGD-gypsum reduced soluble P by 58–67% compared to untreated litter in 1st water extraction. • Shift in P fractions in PL was observed due to FGD-gypsum addition. Phosphorus (P) runoff from agricultural lands receiving poultry litter (PL) poses a major environmental challenge. Application of flue-gas-desulfurization (FGD)-gypsum produced from coal power plants in agricultural lands has shown promise to reduce P losses. However, no information is available about the effectiveness of FGD-gypsum addition in reducing P solubility when applied as an in-house amendment. Hence, the objectives of this study were to understand a) effectiveness of FGD-gypsum as a litter amendment in reducing P loss risk; and b) how FGD-gypsum amendment in PL alters the distribution of P forms. Broiler chickens were raised for five flocks in seven individual litter treatments replicated four times in a randomized complete block design. Based on the FGD-gypsum addition, the PL treatments were broadly classified as FGD-gypsum treated and untreated. Toxic metal concentrations were analyzed in FGD-gypsum as well as the treatments. Sequential water extractions were performed to understand P solubility. Litter P fractionation was performed to identify bioavailable P (Water-P), labile P (NaHCO 3 -P), aluminum/iron chemisorbed P (NaOH-P), and mineral occluded P (HCl-P). Results indicated significantly higher soluble P in all untreated than in all FGD-gypsum treated litters in the initial water extraction. The FGD-gypsum treated litters reduced soluble P by 58 to 67% in the 1st water extraction compared to untreated litters. Fractionation study revealed lower proportion of Water-P and higher proportion of NaHCO 3 -P and HCl-P in all FGD-gypsum treated than in untreated litters. This study suggests reuse of FGD-gypsum in broiler houses can help reduce P mobility without any toxic metals concerns. [ABSTRACT FROM AUTHOR]

A wet electrostatic precipitator (WESP) is typically installed downstream of wet flue gas desulfurization (WFGD) to remove fine particles and sulfuric acid mists from flue gases in coal-fired power plants. The emission reduction characteristics of multiple pollutants and the energy consumption data of 214 sets of WESPs (94 sets of metal plate WESPs, 111 sets of conductive Fiber Reinforced Plastic WESPs, and 9 sets of flexible plate WESPs) were tested and analyzed, and the results showed that: WESPs had a high removal efficiency on PM, PM2.5, SO3, droplets and Hg, and mostly concentrated in ≥75%, ≥70%, ≥60%, ≥70% and ≥40%, respectively. The outlet pollutant concentrations were mostly concentrated in ≤5 mg/m3, ≤3 mg/m3, ≤5 mg/m3, ≤15 mg/m3 and ≤5 μg/m3, respectively. Specific power consumption and specific water consumption were concentrated in the range of 0.5~2.5 × 10−4 kWh/m3 and ≤10 × 10−6 t/m3. The correlation analysis of multiple pollutant's removal performance was studied and the quantitative evaluation index requirements of high efficiency WESPs were determined in this paper. The high efficiency indexes of WESPs, such as PM emission concentration, SO3 emission concentration, PM removal efficiency, SO3 removal efficiency, pressure drop, air leakage rate and specific power consumption, were ≤2.50 mg/m3, ≤2.50 mg/m3, ≥90%, ≥85%, ≤200 Pa, ≤0.5% and ≤1.3 × 10−4 kWh/m3, respectively. The high efficiency indexes of specific water consumption for metal plate WESPs and FRP WESPs were ≤2.50 and ≤0.66 × 10−6 t/m3, respectively. This study can provide valuable reference for the following energy conservation and efficiency improvement of ultra-low emission units. [ABSTRACT FROM AUTHOR]

Flue gas desulfurization gypsum (FGD gypsum) is obtained from the desulphurization of combustion gases in fossil fuel power plants. FGD gypsum can be used to produce anhydrite binder. This research is devoted to the investigation of the influence of the calcination temperature of FGD gypsum, the activators K2SO4 and Na2SO4, and their amount on the compressive strength of anhydrite binder during hydration. The obtained results showed that as the calcination temperature increased, the compressive strength of anhydrite binder decreased at its early age (up to 3 days) and increased after 28 days. The compressive strength of the anhydrite binder produced at 800 °C and 500 °C differed more than five times after 28 days. The activators K2SO4 and Na2SO4 had a large effect on the hydration of anhydrite binder at its early age (up to 3 days) in comparison with the anhydrite binder without activators. The presence of the activators of either K2SO4 or K2SO4 almost had no influence on the compressive strength after 28 days. To determine which factor, the calcination temperature of FGD gypsum (500–800 °C), the hydration time (3–28 days) or the amount (0–2%) of the activators K2SO4 and Na2SO4, has the greatest influence on the compressive strength, a 23 full factorial design was applied. Multiple linear regression was used to develop a mathematical model and predict the compressive strength of the anhydrite binder. The statistical analysis showed that the hydration time had the strongest impact on the compressive strength of the anhydrite binder using activators K2SO4 and Na2SO4. The activator K2SO4 had a greater influence on the compressive strength than the activator Na2SO4. The obtained mathematical model can be used to forecast the compressive strength of the anhydrite binder produced from FGD gypsum if the considered factors are within the same limiting values as in the suggested model since the coefficient of determination (R2) was close to 1, and the mean absolute percentage error (MAPE) was less than 10%. [ABSTRACT FROM AUTHOR]

Adsorbent injection into flue ducts is an effective technology for controlling gaseous pollutant in coal-fired power plants. This study proposed a new technique of injecting dechlorinater into flue duct for HCl removal in order to realize the wet flue gas desulfurization (WFGD) wastewater sequestration and upgrade the gypsum quality, known as the source dechlorination method. Four alkaline-based adsorbents of CaO, Ca(OH)2 + 5 % NaOH, ethanol-modified CaO, and NaHCO3 were developed and investigated in a pilot scale 6 kW coal-fired circulating fluidized bed (CFB) combustion system for capturing flue gas HCl. The physical and chemical properties of the adsorbents were characterized to explore the reaction mechanisms affected by the adsorbent size and its distribution, active component loading, micro-structure, morphology, and crystal structure. The influences of the injection amount, resident time and flue gas temperature on the HCl removal efficiency were carried out, the dechlorination mechanism of the ethanol-modified CaO were discussed. The distribution of flue gas chlorine species across the air pollutant control devices (APCD) were obtained. This study provides basis for developing the technology of injecting dechlorinater into flue gas for HCl removal. [ABSTRACT FROM AUTHOR]

In the presented study, ye'elimite-aluminate-calcium (YAC) cement was synthesized. Complete synthesis of crystalline phases was achieved at a temperature of 1300 °C, which is 150 °C lower than the temperature standardly used in the processes of obtaining calcium aluminate cements (CAC). The greatest amount of ye'elimite phase (Klein complex), roughly 87% by mass, was acquired utilizing a sulphur ion transporter derived from artificial dihydrate gypsum obtained in the flue gas desulphurization process (variation I). In the case of anhydrite, the amount of synthesized crystalline ye'elimite in the clinker was 67% by weight (variant II). Depending on the synthesis conditions in the clinkers, the quantity of obtained calcium aluminates (C12A7, CA, and CA2) ranged from 20 to 40% by weight. Studies on the hydration process of YAC cement samples showed that the main products are hydrated calcium aluminates and dodecahydrate calcium alumino-sulphate. In sinters of YAC and OPC, no crystalline ettringite was observed. Hydration analysis of Chinese cement revealed the presence of crystalline ettringite and dodecahydrate calcium alumino-sulphate, as well as hydrated calcium silicates of the CSH type accompanied with pseudo-crystalline Al(OH)3. The obtained clinkers from variants I and II constitute a special binder, which, due to its phase composition after hydration, can be used in the construction of reactors for biogas production in eco-energy applications. [ABSTRACT FROM AUTHOR]

Efficient capture of sulfur dioxide (SO 2) in the preheater of the cement production system is the key to achieving process compatible flue gas desulfurization (FGD). Herein, the rapid oxidation of trace SO 2 over V 2 O 5 -based catalysts in the preheater environment was realized to enhance the SO 2 capture capacity of limestone in raw meal, and the catalytic efficiency was further improved by 45.2%, 56.1% and 61.9% after introducing TiO 2 /MnO 2 /CeO 2 as cocatalysts, respectively. The V 2 O 5 -based catalysts had superior catalytic behavior only when the flue gas temperature exceeded 500 °C, while the composition variation of flue gas had a minor influence on SO 2 oxidation. Finally, a maximum SO 2 oxidation efficiency of 68.1% was achieved in the presence of 4.0% O 2 , 25.0% CO 2 and 15.0% H 2 O at 600 °C. Furthermore, the mechanism of SO 2 catalytic oxidation over V 2 O 5 -based catalysts was deduced based on the results of XRD, BET, XPS and Raman, and V5+ was identified as the primary vanadium species for SO 2 oxidation. The results provide a deeper insight into the catalytic oxidation of SO 2 in the preheater environment, and then facilitate the improvement of process compatible FGD and available dry FGD technologies for cement industry. [Display omitted] • V 2 O 5 co-catalyzed by TiO 2 /MnO 2 /CeO 2 were prepared for rapid oxidation of trace SO 2. • Catalytic efficiency of V 2 O 5 -based catalysts was investigated. • Factors influencing the oxidation efficiency of trace SO 2 were studied. • 68.1% of SO 2 was oxidized in preheater environment within 1.0 s • Catalytic mechanism and pathways of SO 2 oxidation were proposed. [ABSTRACT FROM AUTHOR]

Air pollution sourced from untreated sulfur dioxide-rich flue gas is one of the major environmental and human health issues. Throughout the years, many sulfur dioxide removal technologies have been invented and implemented on a wide scale. Despite the high sulfur dioxide removal efficiency of conventional treatment methods, such as limestone-gypsum desulfurization and spray dry absorption, they generate a large number of secondary sulfur-containing by-products. Thus, sulfur dioxide catalytic reduction, with the help of suitable reducing agents, is sustainable with acceptable desulfurizing efficiency while recovering valuable solid sulfur. Herein, we review advances in sulfur dioxide catalytic reduction with critical insights contributed by internal and external factors. Sulfur dioxide catalytic reduction is a regenerative desulfurization treatment with lower space requirement and water consumption, simultaneously transforming waste sulfur dioxide to elemental sulfur. Catalytic sulfur dioxide reduction to sulfur via transition metal-based catalysts (copper-alumina and nickel-alumina) and sulfided metal-based catalysts (cobalt-molybdenum/ γ -alumina) appeared to be highly promising for complete sulfur dioxide conversion (100%) while maintaining high sulfur selectivity (more than 99.5%). High industrial and market demands for solid sulfur have also imposed great opportunities to advance this technology. However, the critical weaknesses of sulfur dioxide catalytic reduction are low process maturity and relatively energy-intensive, which is threatened by the high performance of conventional flue gas desulfurization and energy-efficient emerging desulfurization methods. Hence, several strategic directions through threat, opportunity, weakness, and strength analysis (TOWS) are discussed in-depth based on the strength, weakness, opportunity, and threats (SWOT) findings. In realizing environmental sustainability and a circular economy, sulfur dioxide catalytic reduction is a promising method to mitigate sulfur dioxide pollution while transforming waste-to-product, and this study serves as a guide to making sulfur dioxide catalytic reduction a mainstream desulfurization technology. [Display omitted] [ABSTRACT FROM AUTHOR]

The purpose of this research is to assess the yield and reaction rate potential of carbon dioxide (CO2) sequestration through mineralisation using readily available and inexpensive resources by exploiting waste materials. In this case, a blend of four different kinds of ashes and combustion by-products were used, namely, coal fly ash (CFA), flue gas desulphurization (FGD) residues, municipal solid waste incineration fly ashes (MSWI FA) and bottom ash (MSWI BA), produced at the same location. To highlight the impact of these materials on the carbonation process, various factors were analysed, including particle size distribution, immediately soluble contents, mineralogy, particles' detailed structure, and chemical composition. After preparing the samples, two carbonation processes were tested: natural carbonation and accelerated carbonation. To evaluate the impact of the water content on the reaction rate and yield of the mineral carbonation, various liquid-to-solid (L/S) ratios were used. The results demonstrate that the water content and pressure play a significant role in the CO2 sequestration during the accelerated carbonation, the higher the L/S, the greater the yields, which can reach up to 152 g CO2/kg with MSWI FA, while no substantial difference seems to emerge in the case of the natural carbonation. [ABSTRACT FROM AUTHOR]

The circulating fluidized bed flue gas desulfurization (CFB-FGD) process is a promising semi-dry flue gas desulfurization technology. The gas-droplet flow characteristics and droplets evaporation characteristics are critical to improving the desulfurization efficiency of the FGD tower. The effects of droplet parameters, including spray droplet diameter, spray droplet velocity, spray droplet mass flow rate and spray angle are investigated. Two evaluation indices, the coefficient of variation of droplet concentration (CV) and droplet mass-weighted life, are adopted to evaluate mixing degree of gas-droplet and droplet evaporation time, respectively. Results show that as the spray droplet diameter increases from 40 µm to 80 µm, the amount of water droplets trapped by tower wall increases from 3% to 21%. Increasing the spray droplet velocity and spray droplet mass flow rate could effectively increase the turbulent kinetic energy, which could improve the turbulent mixing ability. Moreover, droplet with smaller diameter and high velocity are beneficial to improving the temperature distribution uniformity. When the spray droplet mass flow rate exceeds 2.7 kg/s, the temperature in the tower would be lower than the dew point temperature, resulting in corrosion of the tower wall. Furthermore, the evaporation rate of droplets decreases with the increase of droplet diameter, spray droplet velocity and spray mass flow rate, while increases with the increase in the spray angle. This study would provide a better reference for the optimum operating scheme in practical applications. [Display omitted] • A 3D model was established to simulate droplet evaporation process in CFB-FGD tower. • Gas-droplet mixing and droplet evaporation time are analyzed with evaluation indices. • Smaller droplets are beneficial to improving the temperature distribution uniformity. • Lower droplet velocity and smaller droplet mass increase the droplet evaporation rate. • Appropriate spray angle improves the two-phase mixing and prolongs droplet lifetime. [ABSTRACT FROM AUTHOR]

An effective strategy for achieving cost-effective and environmentally friendly desulfurization wastewater in coal-fired power plants involves the incorporation of desulfurization wastewater into the slag water system. The objective of this study was to analyze the corrosion behavior of Q235-A slag-picker shell material upon the introduction of FGD wastewater into the slag water system. The dynamic weight loss method, electrochemical testing method and microscopic phase characterization were employed to investigate the impact of varying chloride ion concentrations (ranging from 1000 mg/L to 30,000 mg/L) of flue gas desulfurization wastewater (FGD wastewater) on the corrosion of Q235-A slag-picker shell material. The test results indicate that as the concentration of chloride ions increases, the corrosion rate increases from 1.1487 mm/a to 1.5590 mm/a when the concentration is less than 10,000 mg/L. However, when the concentration exceeds 10,000 mg/L, the corrosion rate decreases from 1.559 mm/a to 1.0393 mm/a. The corrosion rate is above 1 mm/a at all concentrations. As the Cl− concentration, the quality of the corrosion product film initially increases and then decreases. The primary components of the corrosion product are α- FeOOH, γ-FeOOH, β-FeOOH, Fe3O4 and γ-Fe2O3. [ABSTRACT FROM AUTHOR]

The introduction of the European Union's climate change legislation and the intended use of renewable energy sources instead of fossil fuels will significantly reduce the production of flue gas desulfurization (FGD) gypsum used as the raw material for gypsum mortar plasters' production. This has forced mortar producers to look for alternative materials, including gypsum–cement composites. This work investigated the mechanical strength and linear extension of four gypsum–cement mortars with the gypsum content reduced to 30%. The authors showed that the cement admixture of 6 to 12% introduced into the prepared mortars resulted in the formation of gypsum–cement mortars, which fulfill the requirements of the EN 13279-1:2008 standard concerning mechanical strength. This publication took into account the use of scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffractometry to characterize the chemical and phase composition of the mortars up to 180 days of dry air curing and increased relative humidity (RH) conditions. The formation of thaumasite, ettringite, and mixed ettringite–thaumasite phases was interesting because of their deleterious effect on the durability of plaster mortars. [ABSTRACT FROM AUTHOR]

The chemical properties of limestone have been the subject of several studies in recent years, highlighting its importance in various industrial applications. The present study focuses on six limestone samples from three geographical regions in Nigeria (Ashaka, Mfamosing, and Nkalagu). The analyses of their chemical composition using the Loss on Ignition Test and X-Ray Fluorescence Spectrometry was successfully carried out. Results of the study show that CaO is the main component, comprising between 60.054 % and 78.632 % of the samples. Values of Loss of Ignition (LOI) ranged from 30.820 % to 33.280 % while SiO2 composition ranged between 5.095 % to 12.238 %. Other oxides detected, include Al2O3 and Fe2O3, which make up less than 1 % of the composition. Obtained values were compared to Limestone standards for various industries and findings indicate that the Ashaka, Mfamosing, and Nkalagu limestone samples are of high purity and suitable for use in various industrial fields, including the steel industry, manufacture of bleaching powder, manufacture of calcium carbide, sugar industry, textile manufacture, cement industry, agricultural practice (soil liming), and flue gas desulphurization. Thus limestone deposits from Ashaka, Mfamosing, and Nkalagu has more potential and application uses beyond cement production which they are currently used for. [ABSTRACT FROM AUTHOR]

In this work, we report pilot-scale tests on a new design of Y-type corrugated polylactic acid (PLA) packing (Prototype FT.Y), produced by an innovative additive manufacturing process consisting of a one-step 3D foam-printing process. The design characteristics of the packing and the surface texture of the prototype, which is analyzed with optical measurements, are presented. The performances of the FT.Y packing are characterized and compared with those of a benchmark commercial Mellapak 250Y packing, through experimental tests aimed to estimate pressure drops and mass transfer coefficients. The new packing is also tested for a reference absorption case study, the wet Flue Gas Desulfurization (wet-FGD), for its large application in the process industry and as a lab testing method. The 3D foam printing technology allows for an easy tailor-made design of the packing, providing lower weights and interesting surface properties. These translate in low pressure drops and high mass transfer coefficients, which are comparable or superior to those of the Mellapak 250.Y. Indeed, the FT.Y packing provides high liquid-film mass transfer coefficients, which allows desulfurization efficiencies up to 42 % higher than those expected for the benchmark packing. Beyond the potential manufacturing advantages provided by the 3D-foam printing, the FT.Y packing performances make this unit a valuable alternative for process intensification in absorption and distillation processes, especially in those cases when the liquid-film mass transfer resistance has a relevant role in the process design. • 3D foam-printing enabled to enhance the surface and wettability properties of FT.Y. • The k L a e coefficient for FT.Y was up to 45 % more than its homologous M250. Y packing. • The FT.Y gas capacity was similar to M250. Y with a flooding limit at 650 Pa/m. • The packed-column with FT.Y allows FGD efficiencies up to 42 % more than M250. Y column. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the effects of wet flue gas desulfurization (WFGD) on particulate matter (PM) emissions in coal-fired power plants (CFPPs) using an electrical low-pressure impactor (ELPI). The investigation was conducted on five industrial CFPPs of various loads in China to clarify the influence factors of WFGD on PM10 emissions. After WFGD, the proportion of PM2.5 to PM10 in the outlet flue gas increases, which showed that the WFGD system is selective in the capture of PM, with a significant effect on the capture of large particle sizes. The investigation found that four spray layers have a better effect on the capture of particles than two spray layers. Additionally, the investigation also found that unit load is not the main factor affecting the efficiency of PM10 capture by WFGD. Instead, the factors affecting the capture efficiency of PM10 by WFGD are the inlet flue gas temperature and the dust concentration. Relatively higher inlet flue gas temperature and lower inlet dust concentration will both result in higher emission of PM0.1~1 from the WFGD outlet. These findings suggest that a matched integration of WFGD and CFPP is essential for ultra-low PM emission control and green industry development. [ABSTRACT FROM AUTHOR]

Soil salinization is one of the major limiting factors for the sustainable development of agriculture in the arid northwest China. Among them, flue gas desulfurization (FGD) gypsum from the coal-fired power plant can be widely used to improve the saline-sodic soil. At the same time, the lignite bioorganic fertilizer (LBF) has also been expected as an effective amendment for the better saline-sodic soil in recent years. However, little is known about the combined application of LBF and FGD gypsum on the physical and chemical properties of saline-sodic soil and sunflower growth. In this study, a two-year field experiment was conducted in 2021-2022, in order to investigate the effect of combining both LBF and FGD gypsum on the saline-sodic soil quality, crop yield, water use efficiency (WUE), and PFPn (PFPn) in the sunflower farmland at the Hetao Experimental Station of China Agricultural University, located in the Bayannur City, Inner Mongolia Autonomous Region, China. Soil samples of 0-40 cm soil layer were collected at the sunflower maturity stage. The sunflower yield, WUE, and PFPn were measured at the same time. Six treatments were considered, i.e., a chemical fertilizer treatment (CK), and 2 t/hm² LBF combined with 0 (LBF), 5 (LBF+F5), 10 (LBF+F10), 15 (LBF+F15), and 20 (LBF+F20) t/hm² FGD gypsum application treatments. The results showed that the LBF treatment decreased the average content of Na+ by 23.33% in the 0-40 cm soil layer in 2022, compared with the CK treatment, but there was no effect on the other water-soluble ions. The LBF combined with the FGD gypsum treatments increased the average contents of Ca2+, SO42− and Mg2+ by 265.58%, 73.77%, and 275.36%, respectively, compared with the CK, whereas, there was the a decrease in the average contents of Na+ and CO32−+HCO3− by 43.60% and 35.07% in 0-40 soil layer. The LBF combined with the FGD gypsum treatments significantly decreased the average soil pH by 0.29-0.88 in the 0-20 cm soil layer. The soil organic matter content in the 0-20 cm soil layer was higher than that in the 20-40 cm soil layer. The LBF treatment significantly increased the soil organic matter content by 39.89%-131.65% in the 0-20 soil layer in 2021-2022. In addition, the LBF combined with FGD gypsum treatments decreased the soil ESP and soil bulk density by 18.34%-43.42%, and 5.91%-11.06% in the 0-40 cm soil layer, respectively, compared with the CK. The LBF+F10, LBF+F15, and LBF+F20 treatments increased the soil aggregate mean weight diameter by 34.57%, 136.78%, and 121.26%, respectively, but there was no effect on the soil percentage aggregate destruction. Although the application of FGD gypsum decreased the soil pH and ESP, however, the excessive application of FGD gypsum would increase the soil salt content, which may inhibit the sunflower growth and yield improvement. The LBF+F10 treatment increased the sunflower yield, WUE, and PFPn by 44.45%, 44.62%, and 80.46%, respectively, compared with the CK. In general, the combination of 2 t/hm² LBF and 10 t/hm²FGD gypsum shared the greatest effect on the physical and chemical properties of saline-sodic soil, indicating the largest sunflower yield, WUE, and PFPn . The finding can provide the scientific implication for the saline-sodic soil remediation and crop productivity improvement of salinized farmland in HID. [ABSTRACT FROM AUTHOR]

Gypsum modification is an effective strategy to improve the water resistance of magnesium oxychloride cement paste (MOCP), but its early-ages performance evolution has not received much attention. The exothermic characteristics and hydration kinetic parameters of MOCP with different contents and types of gypsum are investigated. The results show that the incorporation of gypsum to the MOCP reduces the cumulative heat release of the MOCP and prolongs the induction and acceleration periods. The hydration kinetic parameters also show that the scale factor (A) of MOCP decreases with increasing gypsum content. Incorporation of natural gypsum (NG) to MOCP reduces its nucleation rate and growth rate, while an appropriate amount of flue gas desulfurization gypsum can provide nucleation sites and increase its growth rate. The early-age compressive strength of the gypsum-modified MOCP is reduced due to the reduction in the reaction product (5-phase), but NG can act as a micro-aggregate to alleviate its negative impact on the sample strength. [ABSTRACT FROM AUTHOR]

As the main form of power generation in China, thermal power generation will rely on coal re- sources for a long time, which will cause waste gas pollution such as sulfur dioxide. For flue gas desulfurization, wet desulfurization technology is a common means, but the following is the treatment of desulfurization wastewater. The removal of chloride ions in wastewater by solvent extraction was investigated. Through single factor experiments, the effects of diluent types, modifier types, the proportion of each component of extraction solution, and the proportion of extraction solution to water phase (O/A) on the removal efficiency of chloride ions in wastewater were investigated. In addition, NaOH with a mass fraction of 15% was used as the stripping agent and mixed with the extraction solution in the ratio of 1: 6 for secondary stripping, and the total stripping efficiency could reach 77%. Through four consecutive experiments of regeneration and reuse of extraction solution, it could be seen that 15% NaOH has excellent stripping effect and good reusability of extraction solution, and its extraction performance has not changed significantly after repeated utilization. [ABSTRACT FROM AUTHOR]

The kinetics of oxidation of ammonium sulfite from flue gas desulfurization by ammonia process was studied by changing initial ammonium sulfite concentration, pH, air flow rate, temperature, and concentration of ammonium sulfate in a bubble reactor. The experimental results show that the oxidation rate of ammonium sulfite decreased with the increase of pH but increased with the increase of temperature and airflow rate when the concentration of ammonium sulfate is 0.15 mol/L, temperature of 25–60°C, and an airflow rate of 150–400 L/h. When the concentration of ammonium sulfate increases from 0.2 to 1.0 mol/L, the oxidation rate of ammonium sulfite decreases. At pH 5.0, the activation energy of the apparent oxidation is 26.40 kJ/mol. A kinetics model containing SO32−, SO4, and O2 is used to simulate the oxidation of ammonium sulfate. The results can provide a theoretical basis for the uncatalyzed oxidation of ammonium sulfite in the process of wet ammonia desulfurization process. [ABSTRACT FROM AUTHOR]

The removal of high concentration flue gas sulfur dioxide (SO2) using manganese carbonate ore desulfurization (MCO-FGD) is a promising route that combines economic benefits and pollution control. However, the problems of intermediate oxidation and by-product control have plagued the industrial application of the MCO-FGD technique for a long time. Based on the fact that there is symbiosis of manganese and iron in natural manganese ore, in this study, small amounts of Fe(III) and MnO2 were introduced into the MCO-FGD reaction system to enhance the oxidation of SO2 to SO4− and suppress the manganous dithionate (MnS2O6) by-product generation. The results suggested that the addition of Fe(III) led to the generation of potent oxidant Mn(III) in the reaction system, which accelerated the generation of SO3−• radicals and, thus, enhanced the oxidation of SO2. Under the optimum reaction conditions, the 2.0% of inlet SO2 could be removed to 62 ppm, obtaining 90.1% manganese leaching efficiency, and the concentration of MnS2O6 in the desulfurized liquid was kept below 2.5 g/L after a six-stage desulfurization. The results are of great importance for the sustainable development of the manganese metallurgical industry, which provides theoretical and technical support for the recycling of sulfur and manganese. The influences of different operational conditions on SO2 removal, the catalytic mechanism, and manganese leaching were studied to provide theoretical and technical support for resourceful MCO-FGD technology. [ABSTRACT FROM AUTHOR]

• Heavy metal pollution risk of desulfurized steel slag (DS) as soil amendment was evaluated both in field and pot experiments. • The addition of DS could increase the content of Cr but do not increase the contents of Cu, Zn, Cd, and Pb in soil. • DS application could alter bioavailable and chemical forms of heavy metals in soil and fulvic acid could further reduce the heavy metal pollution risk of DS in agricultural use. • The use of DS in agriculture is safe and feasible technology if it was applied properly. The by-product of wet flue gas desulfurization, desulfurized steel slag (DS), had chemical characteristics like natural gypsum that can be used to improve saline-sodic soil. However, contamination risk of heavy metals for cycling utilization of DS in agriculture was concerned mostly. Both pot and field experiments were conducted for evaluating the potential pollution risk of DS as the amendment of saline-sodic soil. Results showed that application of DS decreased the contents of Cd, Cu, Zn, and Pb, while significantly increasing chromium (Cr) content in DS-amended soils. The field experiment demonstrated that the migration of heavy metals (Cd, Zn, Cu, and Pb) in the soil profile was negligible. The application of DS at the dosage of 22.5–225 tons/ha significantly increased the Cr content in alfalfa (Medicago sativa L.) but lower than the national standard for feed in China (GB 13078-2017). DS altered the chemical fraction of heavy metals (Zn, Cu, and Pb), transferred exchangeable, reducible into oxidizable and residual forms in DS-amended soil. Application of DS combined with fulvic acid (FA) could effectively reduce the movement of heavy metals in soil and the accumulation of Cr in alfalfa. Based on our results, DS was a safe and feasible material for agricultural use and presented relatively little pollution risk of heavy metals. However, the results also showed that DS to a certain extent had a potential environmental risk of Cr if larger dosages of DS were used. [Display omitted] [ABSTRACT FROM AUTHOR]

The interaction of CaO and Ca(OH)2 with solvated or gaseous SO2 plays a crucial role in the corrosion of urban infrastructure by acid rain or in the removal of SO2 from flue gas. We carried out a combined spectroscopic and theoretical investigation on the interaction of SO2 with a CaO(001) single crystal. First, the surface chemistry of SO2 was investigated at different temperatures using polarization‐resolved IR reflection absorption spectroscopy. Three species were identified, and an in‐depth density functional theory study was carried out, which allowed deriving a consistent picture. Unexpectedly, low temperature exposure to SO2 solely yields a physisorbed species. Only above 100 K, the transformation of this weakly bound adsorbate first to a chemisorbed sulfite and then to a sulfate occurs, effectively passivatating the surface. Our results provide the basis for more efficient strategies in corrosion protection of urban infrastructure and in lime‐based desulfurization of flue gas. [ABSTRACT FROM AUTHOR]

[Display omitted] • A promising route for resource utilization of semi-dry FGD ash was proposed. • Subcritical hydrothermal technology was employed for the oxidation of CaSO 3. • The subcritical hydrothermal oxidation macroscopic kinetics was investigated. • The oxidation ratio of CaSO 3 was 89.83% with the optimized parameters. • The reaction was co-controlled by the oxygen diffusion and CaSO 4 precipitation. Realization of low temperature and high efficiency oxidation of CaSO 3 is the key to solve the issue of ecological hazards caused by semi-dry sintering flue gas desulfurization ash. The subcritical hydrothermal technology was employed for the oxidation of CaSO 3 , achieving 89.83% of CaSO 3 at 180 °C, 2 MPa for 120 min with a solid-to-liquid ratio of 1:20. The macroscopic oxidation kinetics of CaSO 3 in the subcritical hydrothermal reaction system was investigated. A mathematical model was established, incorporating the intrinsic reaction, CaSO 3 dissolution, oxygen diffusion and CaSO 4 precipitation. It was concluded that the macroscopic oxidation of CaSO 3 was co-controlled by the oxygen diffusion and CaSO 4 precipitation. Subcritical hydrothermal technology promises not only higher efficiency, but more importantly, potentially "one-step" preparation of CaSO 4 whiskers, enabling cost-effective and high value-added resource utilization of the semi-dry FGD ash. [ABSTRACT FROM AUTHOR]

The large amount of discharge and accumulation of red mud and steel slag has led to the waste of land resources and serious environmental pollution problems. Therefore, the utilization of a large amount of red mud and steel slag in reasonable fields is an urgent problem. At present, the main practical methods include using red mud as a substitute for cement or raw material in cement clinker production and grinding steel slag as a mineral admixture or directly replacing fine aggregates. However, experimental studies on the simultaneous use of large amounts of red mud and steel slag in concrete are extremely limited. In this paper, red mud was used to replace cement (40%–60%) and steel slag to replace fine aggregate (50%–100%) to prepare steel slag fine aggregate red mud–based concrete (SFA-RM concrete). In addition, flue gas desulphurization gypsum (FGDG) was added as a sulfate activator in the concrete to stimulate the potential cementitious activity of red mud and steel slag to prepare the FGDG-activated SFA-RM concrete with improved strength. A total of 18 concrete mixes with different proportions of red mud, steel slag, and gypsum were designed and the mechanical properties, workability, hydration products, and microstructure of these concretes were studied. The results showed that the mechanical properties of FGDG-activated SFA-RM concretes were excellent, the 60 day compressive strength of the SFA-RM concrete reached 43.8 MPa, and the compressive strength of FGDG-activated SFA-RM with 15% gypsum and 100% replacement rate of steel slag improved to 47.1 MPa, which were both better than ordinary concrete. Moreover, the results of X-ray diffraction (XRD) and scanning electron microscope (SEM) tests indicated that the hydration products of concrete mainly included Ca(OH)2 , C-S-H gel, ettringite, and zeolite, with small and few micropores as well as dense microstructure. [ABSTRACT FROM AUTHOR]

The synthesis methods of sulfoxide compounds in recent years were reviewed in terms of whether they were in line with the concept of green chemistry, whether the selectivity and conversion rate were efficient, and whether the synthesis methods were novel. Among them, the most common synthesis method is sulfide oxidation, and after oxidation of oxide system, only sulfoxide is generated, and the yield is guaranteed; Friedel-Crafts sulfinylation reaction realizes the high-selectivity synthesis of pyrrole and sulfonamide for the first time. Visible light-catalyzed synthesis of sulfoxide only requires air as an oxidant, and the reaction conditions are simple and environmentally friendly, which is worthy of vigorous promotion. Since sulfoxide can form complexes with sulfur dioxide and nitrogen oxides in flue gas, sulfoxide is widely used in the field of flue gas desulfurization and denitrification. The rate can reach more than 90%. The system of sulfoxide, diol and diamine is mainly discussed, which has the best absorption effect and is of great significance for industrial production. [ABSTRACT FROM AUTHOR]

Steel slag (SS) has been largely discharged but little utilized, causing an environmental problem in China. In this paper, SS-based composite cementitious materials with high strength were prepared by the high volume of SS (≥40%), granulated blast-furnace slag (GBFS), fly ash (FA), flue gas desulfurization gypsum (FGDG) and cement to promote the effective utilization of SS. The hydration and hardening properties were studied through setting time, compressive strength, length change, isothermal calorimetry (IC), X-ray diffraction (XRD), mercury intrusion porosimetry (MIP), and scanning electron microscopy equipped with energy dispersive spectroscopy (SEM-EDS) tests. The results show that SS-based composite cementitious material exhibited a lower hydration heat release, an appropriate setting time, and volume stability. The SS cementitious material with 40% SS could obtain high strength of over 65 MPa at 28 days and 80 MPa at 90 days. The strength value of > 60 MPa is present in the binder, with 50% SS at 56 days. GBFS promotes hydration reactions and the formation of AFt and C-(A)-S-H gel, thus enhancing compressive strength. FA has a beneficial effect on later strength. The small and fine pore structures contribute to the development of strength. The main hydration products of SS composite cementitious materials are C-(A)-S-H gel, and ettringite (AFt), with less Ca(OH)2. The C-(A)-S-H gel with a lower Ca/Si ratio and a higher Al/Ca ratio in cementitious material, promotes mechanical properties. [ABSTRACT FROM AUTHOR]

Low carbon ferrochrome slag (LCFS) is the metallurgical waste slag from the carbon ferrochrome alloy smelting process. Compared with high carbon ferrochrome slag, LCFS has great potential as cementitious material; the chemical compositions of the two types of slag are quite different. In this research, composite cementitious materials are prepared which use low carbon ferrochrome slag and granulated blast furnace slag (GBFS) as the main raw material. Steel slag mud (SSM) and flue gas desulfurization gypsum (FGDG) are used as the activator. In order to find the variety rule of compressive strength on the composite cementitious materials, a three-factor three-level Box-Behnken design is used to discuss the following independent variables: LCFS content, GBFS content, and water-binder ratio. Moreover, the hydration characteristics of the LCFS-GBFS composite cementitious materials is studied in this paper in terms of hydration product, micromorphology, and hydration degree, based on multi-technical microstructural characterizations. The results show that the compressive strength of the LCFS-GBFS composite cementitious materials is significantly affected by single factors and the interaction of two factors. The mechanical property of the mortar samples at 3, 7, and 28 days are 26.6, 35.3, and 42.7 MPa, respectively, when the LCFS-GBFS-SSM-FGDG ratio is 3:5:1:1 and the water-binder ratio is 0.3. The hydration products of LCFS-GBFS composite cementitious materials are mainly amorphous gels (C-S-H gel), ettringite, and Ca(OH)2. With the increase of LCFS content, more hydration products are generated, and the microstructure of the cementitious system becomes more compact, which contributes to the compressive strength. The results of this research can provide a preliminary theoretical foundation for the development of LCFS-GBFS composite cementitious materials and promote the feasibility of its application in the construction industry. Deep hydration mechanism analysis and engineering applications should be studied in the future. [ABSTRACT FROM AUTHOR]

Removal of hydrogen sulfide (H2S) from coke oven gas has attracted increasing attention due to economic and environmental concerns. In this study, tannin extract (TE) absorption combined with binuclear sulfonated phthalocyanine cobalt organic polymer (OTS) and binuclear sulfonated phthalocyanine cobalt (PDS) with a fixed bed reactor is used for removal of H2S. The effect of gas flow rate, concentration of H2S, co-existence of organic sulfide compounds and O2 were investigated. Then, the effect of total alkalinity content of TE, NaVO3, OTS and PDS was studied in detail. The experimental results demonstrated that 100% H2S conversion could maintain for 13 h at a total alkalinity of 5.0 g/L, TE concentration of 4.0 g/L, NaVO3 concentration of 5 g/L, and OTS and PDS concentration of 0.2 g/L and 0.2 g/L, respectively. The OTS and PDS showed synergistic effect on boosting TE desulfurization efficiency. The results provide a new route for the investigation of liquid catalyzed oxidation desulfurization in an efficient and low-cost way. [ABSTRACT FROM AUTHOR]

The performance of a flue gas desulfurization (FGD) system is characterized by SO2 removal efficiency ( Y 1 ) and reagent conversion ( Y 2 ). Achieving a near-perfect reaction environment has been of concern in dry FGD (DFGD) due to the low reactivity compared to the wet and semi-dry units. This study will appraise output responses using modeling by response surface methodology (RSM) and artificial neural networks (ANN) approaches. The impacts of input parameters like hydration time, hydration temperature, diatomite to hydrated lime (Ca(OH)2), sulfation temperature and inlet gas concentration will be studied using a randomized central composite design (CCD). ANN fitting tool mapped the CCD metadata using the Levenberg-Marquardt (LM) algorithm activated by the hyperbolic tangent (tansig) function. The hidden cells ranged from 7 to 10 to ascertain the effect node architecture on modeling accuracy. Validation of each procedure was assessed using root mean square error (RMSE), mean square error (MSE) and R-Squared studies. The outcomes presented a more accurate 5-10-2 ANN model in the mapping of the DFGD from R2 data of Y 1 = 0.993 and Y 2 = 0.9986 with a mapping deviation from the RMSE values of Y 1 = 0.48465; Y 2 = 0.44971 and MSE results of Y 1 = 0.23488; Y 2. = 0.20229. [ABSTRACT FROM AUTHOR]

The segregation behavior and pitting corrosion resistance under simulated flue gas desulfurization (FGD) environment of 254SMO super austenitic stainless steel (SASS) under different cooling rates were investigated by scanning electron microscopy (SEM), backscattering (BSD), electron probe microanalysis (EPMA) combined with electrochemical analysis and XPS. With the increase in cooling rate, the segregation degree of Cr, Mo and Ni in 254SMO decreased first and then increased, the pitting corrosion resistance showed a trend of first increasing and then decreasing, and the passive film was mainly composed of Cr2O3, Cr(OH)3, Fe2O3, Fe(OH)3, MoO3, NiO and NiOOH. At higher or lower cooling rate, the proportion of protective Cr2O3 was less, which led to a decrease in the protection of the passivation film, and the corrosion resistance was reduced. That is, the lightest segregation degree and the best pitting corrosion resistance of 254SMO at 100 °C/min. In addition, the corrosion mechanism of 254SMO in simulated FGD environment was discussed. [ABSTRACT FROM AUTHOR]

Heterogeneous agglomeration (HA) is a very potential technology for coal-fired flue gas treatment. In this paper, the distribution and migration mechanisms of trace elements (TEs) such as Se, As and Pb in CFPPs were studied on a 30,000 m3/hr pilot-scale experimental platform. The influences of HA on the removal efficiency of gaseous and particulate TEs were well analyzed. The results showed that Se, As and Pb were enriched in fly ash, and their sensitivity to particle size is quite different. The content of Se was the highest in PM 1 , reaching 193.04 mg/kg at the electrostatic precipitator (ESP) outlet. The average particle size of the total dust before ESP increased significantly from 21.686 to 62.612 µm after injecting the heterogeneous agglomeration adsorbent, conducive to its further removal by ESP. In addition, the concentrations of gaseous Se, As and Pb in the flue gas decreased after adsorbent spray, and accordingly, their contents in the hierarchical particles increased, indicating that the adsorbent could effectively promote the adsorption of gaseous trace elements in fly ash and reduce the possibility of their escape to the atmosphere. Total concentrations of Se, As and Pb emitted by wet flue gas desulfurization (WFGD) are 0.223, 0.668 and 0.076 µg/m3, which decreased by 59.98%, 47.69% and 90.71%, respectively. Finally, a possible HA mechanism model was proposed, where chemical adsorption, physical condensation and collision agglomeration of gaseous TEs and fine particles with adsorbent droplets occurred to form larger agglomerates. [Display omitted] [ABSTRACT FROM AUTHOR]